Automatic fingerprint scanners are commonly used to obtain an analog or digital image for security, access, verification, or record-keeping applications. In most conventional scanners, a two-dimensional (2D) image of the fingerprint is captured by an imaging device having a matrix of picture elements or pixels arranged as multiple rows and columns. A 2D light-sensitive electronic sensor, such as a charge-coupled device (CCD), is typically used to capture a fingerprint image. However, the cost and size of a typical CCD and associated optics may make it expensive or impractical for use in some constrained physical environments, such as keyboards, laptop a computers, and pointing devices such as a mouse or trackball.
One known system uses a series of thermal sensors configured in a cross-shaped, L-shaped or T-shaped pattern having a single column and a single row. When a user slides his or her finger along the sensors, the column sensors are used to determine the position and speed of the finger, and the row sensors are used to obtain an image of the fingerprint. However, the thermal system does not prevent against possible distortion of the fingerprint image from either the stretching of the skin on the finger or the flattening of the ridges and valleys of the fingerprint due to excess pressure.
There is a need for a small and inexpensive way of scanning a fingerprint in a constrained physical environment which does not distort the fingerprint image.